The core set of seventy-two markers is divided up into twelve color families, each containing six markers per set. Each package contains pre-matched color tone families with three `warm' tones and three `cool' tones.With a broad chisel nib for large area fills and a fine bullet tip for detailed work, these markers are perfect for every papercrafting project. There is also an interchangeable brush tip nib, available separately, which can be used in place of the chisel nib to create some gorgeous effects. The numbers on the end of each Spectrum Noir marker indicate how intense or dark the color is. The numbering system was made for very easy understanding: 1 is very pale, 2 is a bit more intense/dark and 10 is much more intense/dark. The letters on the end of the marker specify the color tone family the marker belongs to. For example, CT = Citrus Yellow, TN = Tan, CR = Coral Red, CG = Citrus Green and so on.